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authorEric Biggers <ebiggers@google.com>2018-11-16 17:26:21 -0800
committerHerbert Xu <herbert@gondor.apana.org.au>2018-11-20 14:26:55 +0800
commit1ca1b917940c24ca3d1f490118c5474168622953 (patch)
tree26cde5a85d0792a8dd709a6f5316f76af8801a35 /include/crypto/chacha.h
parentde61d7ae5d3789dcba3749a418f76613fbee8414 (diff)
crypto: chacha20-generic - refactor to allow varying number of rounds
In preparation for adding XChaCha12 support, rename/refactor chacha20-generic to support different numbers of rounds. The justification for needing XChaCha12 support is explained in more detail in the patch "crypto: chacha - add XChaCha12 support". The only difference between ChaCha{8,12,20} are the number of rounds itself; all other parts of the algorithm are the same. Therefore, remove the "20" from all definitions, structures, functions, files, etc. that will be shared by all ChaCha versions. Also make ->setkey() store the round count in the chacha_ctx (previously chacha20_ctx). The generic code then passes the round count through to chacha_block(). There will be a ->setkey() function for each explicitly allowed round count; the encrypt/decrypt functions will be the same. I decided not to do it the opposite way (same ->setkey() function for all round counts, with different encrypt/decrypt functions) because that would have required more boilerplate code in architecture-specific implementations of ChaCha and XChaCha. Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Acked-by: Martin Willi <martin@strongswan.org> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'include/crypto/chacha.h')
-rw-r--r--include/crypto/chacha.h47
1 files changed, 47 insertions, 0 deletions
diff --git a/include/crypto/chacha.h b/include/crypto/chacha.h
new file mode 100644
index 000000000000..b722a23e54bb
--- /dev/null
+++ b/include/crypto/chacha.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Common values and helper functions for the ChaCha and XChaCha stream ciphers.
+ *
+ * XChaCha extends ChaCha's nonce to 192 bits, while provably retaining ChaCha's
+ * security. Here they share the same key size, tfm context, and setkey
+ * function; only their IV size and encrypt/decrypt function differ.
+ */
+
+#ifndef _CRYPTO_CHACHA_H
+#define _CRYPTO_CHACHA_H
+
+#include <crypto/skcipher.h>
+#include <linux/types.h>
+#include <linux/crypto.h>
+
+/* 32-bit stream position, then 96-bit nonce (RFC7539 convention) */
+#define CHACHA_IV_SIZE 16
+
+#define CHACHA_KEY_SIZE 32
+#define CHACHA_BLOCK_SIZE 64
+#define CHACHAPOLY_IV_SIZE 12
+
+/* 192-bit nonce, then 64-bit stream position */
+#define XCHACHA_IV_SIZE 32
+
+struct chacha_ctx {
+ u32 key[8];
+ int nrounds;
+};
+
+void chacha_block(u32 *state, u8 *stream, int nrounds);
+static inline void chacha20_block(u32 *state, u8 *stream)
+{
+ chacha_block(state, stream, 20);
+}
+void hchacha_block(const u32 *in, u32 *out, int nrounds);
+
+void crypto_chacha_init(u32 *state, struct chacha_ctx *ctx, u8 *iv);
+
+int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
+ unsigned int keysize);
+
+int crypto_chacha_crypt(struct skcipher_request *req);
+int crypto_xchacha_crypt(struct skcipher_request *req);
+
+#endif /* _CRYPTO_CHACHA_H */